Immunoperoxidase and immunofluorescence methods are being employed for the identification of normal and neoplastic human bronchial epithelial cells in tissue specimens and in primary cultures in vitro. Paraffin-embedded specimens of normal human bronchus from 20 patients were examined for the presence of: 1) A, B or H blood group antigens; 2) carcinoembryonic antigen (CEA); 3) alpha fetoprotein (AFP); 4) adrenocorticotropic hormone (ACTH); and 5) human chorionic gonadotrophin (HCG). A, B and H blood group antigens were localized in epithelial cells of the bronchial specimens and not in stromal fibroblasts. As expected, normal bronchial epithelial cells were negative for AFP, ACTH and HCG, although small amounts of CEA were found in the glycocalyx. Large amounts of CEA were detected in human lung tumors. Cultured bronchial epithelial cells also stained positively for A, B or H blood group antigens and fibroblast cells were negative. CEA, AFP, HCG and ACTH were not synthesized by normal bronchial epithelial cells.